Magnetoresistive element and manufacturing method therefor

ABSTRACT

This invention relates to a magnetoresistive element used for a magnetic sensor, etc. A ferromagnetic magnetoresistive element thin film is formed so as to be electrically connected to and so as to overlap the upper end portion of an aluminum wiring metal on a substrate. Through using a vacuum heat treatment with a temperature between 350° and 450° C., a Ni--Al-based alloy is formed at the overlapping portion. Therefore, even when a surface protection film of silicon nitride is subsequently formed by plasma CVD on the substrate, the alloy prevents the nitriding of the upper end portion of the aluminum wiring metal. Accordingly, the surface can be protected from moisture by the silicon nitride film without increasing the contact resistance between the magnetoresistive element thin film and the wiring metal. Instead of the Ni--Al-based alloy, other conductive metals such as TiW, TiN, Ti, Zr, or the like may be used. Also, the surface protection film may be a multi-layered film having a first film containing no nitrogen, such as a silicon oxide film, and a second film of silicon nitride film formed on the first film.

DESCRIPTION

1. Technical Field

This invention relates to a magnetoresistive element and a manufacturingmethod therefor.

2. Background Art

A magnetoresistive element as disclosed in Japanese Laid-open PatentApplication No. 1-125882 has been conventionally used for a magneticsensor, etc.

Generally, in a magnetic sensor using a thin film of magnetoresistiveelement, as shown in FIG. 25, an insulating film 4 is formed on amonocrystal silicon substrate 1 having a circuit element, aluminumwiring metal 9 is formed on the insulating film 4, and a thin film offerromagnetic magnetoresistive element 10 formed of Ni--Fe, Ni--Co orthe like is formed on the aluminum wiring metal 9. The magnetoresistiveelement thin film 10 is disposed on the aluminum wiring metal 9 for thefollowing reason. If the magnetic-resistance element thin film 10 ispriorly formed, a patterning of the aluminum wiring metal 9 issubsequently carried out, and thus an etching of the magnetoresistiveelement thin film 10 must be considered at the patterning step.

The thin film such as Ni--Fe, Ni--Co or the like is very active, so thatit is liable to be oxidized and damaged. Therefore, a surface protectionfilm 11 formed of silicon nitride which can be formed at a lowtemperature is formed on the magnetoresistive element thin film 10. Itis formed in the following manner, for example. The monocrystal siliconsubstrate which is an object on which elements are laminated is insertedinto a vacuum chamber, raw gas (monosilane, nitrogen, ammonia, etc.)flows into the vacuum chamber at 200° to 400° C., and plasma is excitedwith a high-frequency power source to deposit a silicon nitride film(surface protection film 11). Through this process, the surfaceprotection film can be formed without oxidizing the magnetoresistiveelement thin film 10, and in addition the silicon nitride film havingdefects such as pinholes, can be formed as the surface protection film.The bond resistance (contact resistance) between the magnetoresistiveelement thin film 10 and the aluminum wiring metal 9 is ordinarily about1Ω, however, it is experimentally proved that if a silicon nitride filmhaving excellent moisture resistant property is deposited as the surfaceprotection film 11, the bond resistance would be varied to several tensto 1MΩ after deposition of the silicon nitride. For the magnetic sensoras shown in FIG. 25, the result of the contact resistance of Ni--Co/Alwhich is measured before and after a plasma silicon nitride film (P--SiNfilm) serving as the surface protection film 11 is formed is shown inFIG. 26. It is apparent from FIG. 26 that in comparison with the contactresistance before the plasma silicon nitride film is formed, the contactresistance after the plasma silicon nitride film is formed is increasedin two or more orders. This indicates a failure in the electricalconnection of Ni--Co/Al.

An object of this invention is to provide a magnetoresistive element anda manufacturing method for the magnetoresistive element in which anincrease in the contact resistance between a magnetoresistive elementthin film and a wiring metal due to formation of a surface protectionfilm can be inhibited,

DISCLOSURE OF INVENTION

In order to clarify the cause of an increase in the contact resistancedue to formation of the silicon nitride as described above, thevariation of the contact resistance is measured in the same manner underan NH₃ gas atmosphere which is one of atmosphere gases at the formationtime of the plasma silicon nitride. The result is shown in FIG. 27. Thecontact resistance of Ni--Co/Al is varied in about two orders byexposing it to the NH₃ gas atmosphere in comparison with that beforeexposure to the NH₃ gas atmosphere, and thus proving that the increasein contact resistance after the plasma silicon nitride film is formed ismainly caused by the NH₃ gas.

FIG. 28 shows an SIMS analysis result of a bond portion (contactportion) between the magnetoresistive element thin film 10 and thealuminum wiring metal 9 after the plasma silicon nitride film is formed,which was measured using a secondary ion mass spectrometer.

It is proved from FIG. 28 that a large amount of aluminum nitride (AlN)exists at the contact portion. The surface of the aluminum wiring metal9 is exposed to the gas (particularly, ammonia, nitrogen), which isindispensable for the formation of the surface protection film (siliconnitride) 11, at high temperature. Even at the contact portion, which iscovered with the ferromagnetic magnetoresistive element thin film 10thereon, the gas containing nitrogen penetrates through theferromagnetic magnetoresistive element thin film 10 and reaches thesurface of the aluminum wiring metal 9, and thus it is considered thatthe aluminum nitride 15 is formed as shown in a schematic diagram ofFIG. 29. The aluminum nitride 15 has an insulation property, and thiscauses the contact resistance to be increased.

In order to attain the above object, the magnetoresistive elementaccording to this invention includes a substrate, aluminum-based wiringmetal disposed on the substrate, a nickel-based magnetoresistive elementthin film which is electrically connected to the aluminum-based wiringmetal, a barrier film which is formed at the upper portion of theconnection portion between the aluminum-based wiring metal and themagnetoresistive element thin film, and a surface protection film formedof nitride which covers the magnetoresistive element thin film.

In particular, the barrier film is characterized by comprising an alloylayer formed at the connecting portion between the aluminum-based wiringmetal and the magnetoresistive element thin film by conducting a heattreatment before the surface protection film is formed. That is, theheat treatment is conducted before the surface protection film isformed, whereby the magnetoresistive element thin film is diffused intothe aluminum-based wiring metal to form the alloy layer of thealuminum-based wiring metal and the magnetoresistive element thin film.Accordingly, the alloy layer of the aluminum-based wiring metal and themagnetoresistive element thin film as described above is formed at theupper portion of the aluminum-based wiring metal at the connectingportion, so that under the gas atmosphere containing nitrogen at thefilm formation time of the surface protection film, the alloy layerprevents the penetration of the nitrogen therethrough and prohibits theformation of insulating aluminum nitride at the connection portionbetween the magnetic-resistance element thin film and the aluminum-basedwiring metal.

When the magnetoresistive element thin film and the aluminum-basedwiring metal are disposed and connected to each other on the substrate,both are electrically connected to each other while another conductor isinterposed therebetween as the barrier film. Here, in a case where aconductor for connection is disposed on the upper layer side of thealuminum-based wiring metal, the connection conductor is required toinhibit nitrogen from passing therethrough. On the other hand, in a casewhere the connection conductor is disposed at the lower layer of thealuminum-based wiring metal, penetration of the gas containing nitrogenat the contact portion is prevented by the aluminum-based wiring metalserving as the upper layer side. Further, in a case where the connectionconductor is disposed at the lower layer side of the magnetoresistiveelement thin film, non-aluminum-based conductor is selected as theconnection conductor. As the non-aluminum-based conductor, a materialwhich is not nitride or if it is nitride, a nitride film that becomesconductive is selected. With this construction, even when exposed to thegas atmosphere containing nitrogen in the process of forming the siliconnitride film, no insulating AlN is formed at the contact portion betweenthe magnetoresistive element thin film and the connection conductor andthe contact portion between the connection conductor and thealuminum-based wiring metal.

Further, the following manufacturing method may be adopted. That is, themagnetoresistive element thin film and the aluminum-based wiring metalare disposed and electrically connected to each other on the substrate,the connection portion between the magnetoresistive element thin filmand the aluminum-based wiring metal is covered by a silicon oxide filmor an-amorphous silicon film, and the silicon oxide film or theamorphous silicon film is covered by a surface protection film formed ofa silicon nitride film. With this construction, invasion of nitrogenunder the gas atmosphere containing nitrogen when the silicon nitridefilm is formed is prevented by the silicon oxide film or the amorphoussilicon film, and no AlN is formed at the contact portion between themagnetoresistive element thin film and the aluminum-based wiring metal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional sensor of a magnetic view of a firstembodiment;

FIG. 2 is an enlarged view of a D portion of FIG. 1;

FIG. 3 is a plane view showing a contact state between a ferromagneticmagnetoresistive element thin film and an aluminum wiring metal;

FIGS. 4 to 7 are cross-sectional views showing a manufacturing processof the magnetic sensor of the first embodiment;

FIG. 8 is a plane view showing a contact state between conventionalferromagnetic magnetoresistive element thin film and aluminum wiringmetal;

FIGS. 9 and 10 are cross-sectional views showing the contact portionbetween the ferromagnetic magnetoresistive element thin film and thealuminum wiring metal;

FIGS. 11 and 12 are plane views of the magnetic sensor, and FIG. 13 is agraph showing the relationship between a current value and a filmdestruction rate in each construction of FIGS. 11 and 12;

FIG. 14 is a graph showing a measurement result of a contact resistance;

FIG. 15 is a graph showing a measurement result of a contact resistancewhen temperature in a vacuum heat-treatment is varied;

FIG. 16 is a graph showing a measurement result of a sheet resistancewhen a vacuum degree in the vacuum heat-treatment is varied;

FIG. 17 is a graph showing a contact resistance;

FIG. 18 an SIMS analysis result of the contact portion when the vacuumheat-treatment is conducted;

FIG. 19 is a cross-sectional view of the schematic construction of thecontact portion when the vacuum heat-treatment is conducted; and

FIG. 20 is a graph showing the relationship between presence ofNi-Al-based alloy and variation rate of magnetic resistance;

FIGS. 21 and 22 are plane views of a magnetic sensor which is anapplication example of the first embodiment;

FIGS. 23 and 24 are cross-sectional views of another example of themagnetic sensor of the first embodiment;

FIG. 25 is a cross-sectional view of the prior art;

FIGS. 26 and 27 are graphs showing measurement results of the contactresistance;

FIG. 28 is a graph showing an SIMS analysis result of the conventionalcontact portion; and

FIG. 29 is a cross-sectional view of the schematic construction of theconventional portion;

FIG. 30 is a cross-sectional view of a magnetic sensor of a secondembodiment;

FIGS. 31 to 33 are cross-sectional views showing a manufacturing processof the magnetic sensor of the second embodiment;

FIG. 34 is a graph showing a measurement result of the contactresistance;

FIG. 35 is a cross-sectional view of a magnetic sensor of a thirdembodiment;

FIGS. 36 to 38 are cross-sectional views showing a manufacturing processof the magnetic sensor of the third embodiment;

FIG. 39 is a cross-sectional view showing another embodiment of themagnetic sensor of the third embodiment;

FIG. 40 is a cross-sectional view of a magnetic sensor of a fourthembodiment;

FIGS. 41 to 43 are cross-sectional views showing a manufacturing processof the magnetic sensor of the fourth embodiment;

FIG. 44 is a plane view of a magnetic sensor of a modification of thefourth embodiment. FIG. 44 is a plane view of a magnetic sensor ofanother modification of the fourth embodiment;

FIG. 45 is a E--E cross-sectional view of the magnetic sensor;

FIG. 46 is a cross-sectional view of a magnetic sensor of a fifthembodiment; and

FIGS. 47 to 49 are cross-sectional views of a manufacturing process ofthe magnetic sensor of the Fifth embodiment.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

Embodiments of a magnetic sensor according to this invention will behereunder described with reference to the accompanying drawings.

(First Embodiment)

FIG. 1 is a cross-sectional view of the magnetic sensor of the firstembodiment. The ferromagnetic magnetoresistive element thin film 10 andthe signal processing circuit are integrated on the same substrate. FIG.2 is an enlarged view of a D portion of FIG. 1, and FIG. 3 is a planeview of the D portion.

FIGS. 4 to 7 show the manufacturing process of the magnetic sensor.

First, as shown in FIG. 4, a vertical type of NPN bipolar transistor isformed on a main surface of a P-type semiconductor substrate(monocrystal silicon substrate) i using a well-known processingtechnique. That is, on the main surface of the P-type semiconductorsubstrate 1 are formed an N'-type buried layer 2 and an N⁻ -typeepitaxial layer 3. Further, a silicon oxide film 4 is formed on a mainsurface of the N⁻ -type epitaxial layer 3 by a heat oxidation method ora CVD method, the silicon oxidation film 4 is subjected to aphotoetching treatment by a desired circuit pattern, and P⁺ -typeelement separation region 5, P⁺ -type diffusion region 6 and N⁺ -typediffusion regions 7 and 8 are formed by diffusion of impurities. Thatis, the N⁺ -type region is formed by selectively diffusing phosphorusand the P⁺ -type region is formed by selectively diffusing boron usingan ion injection method or a diffusion method. Through the aboveprocesses, the vertical NPN bipolar transistor is constructed by the N⁺-type buried layer 2, the N--type epitaxial layer 3, the P⁺ -typediffusion region 6, and the N⁺ -type diffusion regions 7 and 8, and thistransistor is used to amplify a signal from the ferromagneticmagnetoresistive element thin film 10 as described later.

Subsequently, an opening portion 4a is selectively formed in the siliconoxide film 4 using a photolithography to form a contact portion. Asshown in FIG. 5, a thin film of aluminum wiring metal 9 is deposited onthe main surface of the P-type semiconductor substrate 1 by a depositionmethod or a sputtering method, and this aluminum wiring metal 9 ispatterned by the photoetching treatment. At this time, the end portionof the aluminum wiring metal 9 is so processed that the section thereofis designed in a slant (tapered) form (as represented by a slant portion9a in the figure). That is, a wet-type taper etching is conducted to setan inclination angle θ of the slant portion 9a below 78 degrees, forexample, to 50 degrees. As shown in FIG. 2, the inclination angle θ isdefined as an intersecting angle between the silicon oxide film 4 andthe end surface of the aluminum wiring metal 9.

Thereafter, in order to obtain an ohmic junction between the aluminumwiring metal 9 and a circuit element (silicon) such as a bipolartransistor or the like, a heat-treatment which is called as"alumi-sinter" is-conducted, for example, at 450° C. for 30 minutesunder foaming gas (N₂ +H₂). At this time, an insulating film such as anoxide film or the like is also formed on the surface of the aluminumwiring metal 9.

Subsequently, the P-type semiconductor substrate 1 is disposed in avacuum chamber, and the oxide layer grown on the surface of the aluminumwiring metal 9 is etched by a plasma etching treatment of inert gas (forexample, Ar gas). Thereafter, as shown in FIG. 6, the ferromagneticmagnetoresistive element thin film 10 is deposited on the silicon oxidefilm 4 containing the aluminum wiring metal 9 in the same vacuum chamberwith keeping a vacuum state. Therefore, a metal contact containing nooxide layer is formed at the interface between the aluminum wiring metal9 and the ferromagnetic magnetoresistive element thin film 10. Theferromagnetic magnetoresistive element thin film 10 is formed of aferromagnetic thin film which is mainly composed of Ni and contains Fe,Co, that is, an Ni--Fe or Ni--Co thin film, and its thickness is about500· (200 to 2000Å). In this embodiment, a Ni--Co thin film is used asthe ferromagnetic magnetoresistive element thin film 10, and it is sodesigned as to be thinner than the aluminum wiring metal 9 (see FIG. 2).

As shown in FIG. 7, the ferromagnetic magnetoresistive element thin film10 is etched into a desired bridge pattern by the photoetchingtreatment. At this time, as shown in FIG. 2, the ferromagneticmagnetoresistive element thin film 10 is sufficiently overlapped withthe slant portion 9a of the aluminum wiring metal 9. Through the slantportion 9a, the ferromagnetic magnetoresistive element thin film 10 andthe aluminum wiring metal 9 are electrically bonded to each other. Theend portion of the aluminum wiring metal 9 is designed in the taperedstructure to avoid disconnection between the ferromagneticmagnetoresistive element thin film 10 and the aluminum wiring metal 9.

In this case, the ferromagnetic magnetoresistive element thin film 10serving as a magnetic sensor is formed on the silicon oxide film 4. Theferromagnetic magnetoresistive element thin film 10 is photoetched tohave 10 to 15 μm width, and the length thereof is determined on thebasis of specific resistance, thickness t (see FIG. 2) and width W ofthe ferromagnetic magnetoresistive element thin film 10 to obtain adesired bridge resistance.

Subsequently, The P-type semiconductor substrate 1 formed with theferromagnetic magnetoresistive element thin film 10 is subjected to thevacuum heat-treatment (vacuum annealing) for a constant time (forexample, for 30 minutes). The vacuum heat-treatment is carried out underthe following condition: at a temperature of 350° to 450° C. and under avacuum (for example, below 10₋₂ Torr). At this time, Ni--Al-based alloyas described later is formed at the connection portion of theferromagnetic magnetoresistive element thin film 10 and the aluminumwiring metal 9, and the ferromagnetic magnetoresistive element thin film10 and the aluminum wiring metal 9are electrically connected to eachother through the Ni--Al-based alloy.

Thereafter, as shown in FIG. 1, a surface protection film 11 of siliconnitride is formed using a plasma CVD device. That is, the P-typesemiconductor substrate 1 is kept at the temperature of about 200° to400° C. and gas (monosilane., nitrogen, ammonia, etc.) are supplied, andplasma is excited by a high-frequency power source to deposit a siliconnitride film. Further, only a conductive terminal portion of the surfaceprotection film 11 is etched to form an opening portion, and themagnetic sensor as shown in FIG. 1 is formed.

In the magnetic sensor thus formed, an NPN transistor formed on the mainsurface of the P-type semiconductor substrate 1, a PNP transistor as notshown, a diffusion resistor and a circuit element, such as a condenser,are electrically connected to one another through the aluminum wiringmetal 9 to enable these elements to function as an electrical circuit.Further, the ferromagnetic magnetoresistive element thin film 10 and thecircuit element formed on the main surface of the P-type semiconductorsubstrate 1 are protected from the outside air through the surfaceprotection Film 11 of silicon nitride.

Next, characteristics of the connection portion between theferromagnetic magnetoresistive element thin film 10 and the aluminumwiring metal 9 according to this embodiment will be described.

Now considering resistance Ro of the ferromagnetic magnetoresistiveelement thin film 10, it is represented by the sum of resistanceR_(Ni-Co) of the ferromagnetic magnetoresistive element thin film 10 andcontact resistance Rc of the ferromagnetic magnetoresistive element thinfilm 10 and the aluminum wiring metal 9 (Ro=R_(Ni--Co) +2.Rc).Therefore, in order to set the resistance Ro of the Ferromagneticmagnetoresistive element thin film 10 to a design value, not only theprecision of the pattern processing, but also the contact resistance Rcof the ferromagnetic magnetoresistive element thin film 10 and thealuminum wiring metal must be set to such a small value that theresistance value Ro is determined by only the pattern of theferromagnetic magnetoresistive element thin film 10.

The inventor of this application experimentally investigated whatdetermined the contact resistance of Ni--Co/Al. Conventionally, thecontact resistance between the metal films (aluminum layer wiring) isvaried in accordance with the contact area, and representing contactresistance rate by ρc and the area of the contact portion by A, thecontact resistance Rc is represented by Rc=ρc/A. However, it is foundout that in the structure of Ni--Co/Al group which the contact is madewith, the slant portion in section, the contact resistance is notdependent on the area A, but dependent on only the contact area betweenthe ferromagnetic magnetoresistive element thin film 10 and the slantportion 9a of the aluminum wiring metal. Representing the contactresistance rate of the aluminum wiring metal 9 and the ferromagneticmagnetoresistive element thin film 10 by ρ, the inclination angle of theslant portion 9a of the aluminum wiring metal 9 by θ (see FIG. 2), thethickness of smaller one of the aluminum wiring metal 9 and theferromagnetic magnetoresistive element thin film 10 at the contactportion of the aluminum wiring metal 9 and the ferromagneticmagnetoresistive element thin film 10 (that is, the ferromagneticmagnetoresistive element thin film 10) by t, and the length of thecontact portion by L, the contact resistance Rc of this structure isrepresented by

    Rc=ρc . sinθ/ (t.L)                              . . . (1)

From this, the contact resistance Rc can be set to a desired designvalue. From the equation (1), a device for reducing the contactresistance Rc can be made. That is, as shown in FIG. 3, a recess portion12 is formed at the tip end portion of the aluminum wiring metal 9, andthe ferromagnetic magnetoresistive element thin film 10 is disposed ofthe recess portion 12 to increase the value of L of the equation (1),and thus to reduce Re. As a result, L is equal to L1+L2+L3, and L can bemore lengthened in comparison with a case where no recess portion 12 isprovided. That is, conventionally, the contact with the aluminum wiringmetal is carried out while the line width of the ferromagneticmagnetoresistive element thin film 1 (determined by the design value ofthe ferromagnetic resistance variation rate and the design value of thebridge resistor) is not changed and the aluminum wiring metal 9 is leftband-shaped, so that the contact resistance is high. However, by formingit in a shape as shown in FIG. 3 (shape of recess portion 12), thecontact resistance can be reduced in one or more orders.

The length of each side of the recess portion 12 as shown in FIG. 3 isset to two or more times of the thickness the aluminum wiring metal 9.More specifically, in this embodiment the thickness of the aluminumwiring metal 9 is set to 1 μm, and the length of each side of the recessportion 12 is set to 16 μm. Therefore, the length of each side of therecess portion 12 is set to 16 times the thickness of the aluminumwiring metal 9.

With the structure having such a recess portion 12, although thedirection at the contact portion between the aluminum wiring metal 9 andthe ferromagnetic magnetoresistive element thin film 10 isunidirectional (A direction in FIG. 8) in the conventional structurehaving no recess portion as shown in FIG. 8, in this embodiment, asshown in FIG. 3, both are contacted with each other in three directions(A, B, C directions). In other words, current Flow-in surfaces areformed in the three directions (A, B, C directions).

That is, in the conventional method when the aluminum wiring metal 9 andthe ferromagnetic magnetoresistive element thin film 10 are contacted inone direction, the ferromagnetic magnetoresistive element thin film 10is constricted at the end portion of the contact portion with thealuminum wiring metal 9 as shown in FIG. 9 due to the incident angle ofNi--Co particles to the substrate when the ferromagneticmagnetoresistive element thin film 10 is formed. As a result, thepermissible current capacity is lowered, and thus the ferromagneticmagnetoresistive element thin film 10 may be broken down at theconstricted portion. However, using the construction having the recessportion 12 of this embodiment, the aluminum wiring metal 9 and theferromagnetic magnetoresistive element thin film 10 are contacted witheach other in the three directions. Therefore, even when variationoccurs in the incident angle when the ferromagnetic magnetoresistiveelement thin film 10 is deposited, there exists at least one directionwhere no constriction of the ferromagnetic magnetoresistive element thinfilm 10 occurs as shown in FIG. 10 although there is a constrictiondirection of the ferromagnetic magnetoresistive element thin film asshown in FIG. 9.

Here, the breakdown rate of the ferromagnetic magnetoresistive elementthin film 10 was measured for two cases where two recess portions 12aand 12b are formed as shown in FIG. 11 and where no recess portion isformed as shown in FIG. 12. In FIGS. 11 and 12, the junction between theferromagnetic magnetoresistive element thin film 10 and the aluminumwiring metal 9 is so designed that a wide portion 13 is formed at theend of the ferromagnetic magnetoresistive element thin film 10 and thelength L of the contact portion is made longer to promote the reductionof contact resistance Rc as described above.

The result is shown in FIG. 13, which shows the relationship between acurrent value and a rate at which the ferromagnetic magnetoresistiveelement thin film 10 is burnt out at the end portion of the aluminumwiring metal 9 and broken down. The current value is normalized so thatthe breakdown rate of the structure as shown in FIG. 11 is set to "1".From FIG. 13, it is found out that the breaking current value of theferromagnetic magnetoresistive element thin film 10 at the end portionof the aluminum wiring metal 9 is increased to three or more times byproviding the recess portion. That is, the breaking current value in thecase of providing no recess portion was 0.26 while that in the case ofproviding the two recess portions 12a and 12b was 0.95. That is, thebreaking current value can be increased to 0.95/0.26÷3.6 times. Asdescribed above, the length L of the contact portion is make longer andin addition the aluminum wiring metal 9 and the ferromagneticmagnetoresistive element thin film 10 are contacted with each other toflow current in such a direction that no constriction exists, wherebythe permissible current capacity can be increased.

On the other hand, in a case where the ferromagnetic magnetoresistiveelement thin film 10 and the aluminum wiring metal 9 are contacted witheach other, the slant portion 9a is formed at the tip portion of thealuminum wiring metal 9, and the ohmic junction is formed with thecircuit element by the heat treatment (under foaming gas atmosphere). Inthis process, the surface of the aluminum wiring metal 9 is oxidized,and it serves as a barrier layer when the ohmic junction is formedbetween the ferromagnetic magnetoresistive element thin film 10 and thealuminum wiring metal 9, so that the equation (1) is not satisfied. Inaddition, the contact resistance rate ρc is increased to 10⁻⁴ Ωcm² to10⁻⁵ Ωcm². However, as described above, the contact resistance rate ρccan be set below 10⁻⁵ Ωcm² by etching the oxide layer of the surface ofthe aluminum wiring metal 9. As a result, the contact resistance can bereduced.

FIG. 14 shows the measurement results of the contact resistance value ina case where the oxide layer of the surface of the aluminum wiring metal9 is etched and in a case where no etching treatment is conducted on theoxide layer. As shown in the figure, by etching the oxide layer, boththe contact resistance and the variation of the resistance value arereduced to 1/3 or less. In addition, the contact resistance rate (ρc) isreduced below 10⁻⁶ Ωcm².

Next, the vacuum heat treatment, which is carried out before the surfaceprotection film 11 is formed, will be hereunder described on the basisof various experimental results.

FIG. 15 show a measurement result of the bond resistance (contactresistance) between the ferromagnetic magnetoresistive element thin film10 and the aluminum wiring metal when the temperature in the vacuum heattreatment is varied. It is apparent from the figure that in order tosuppress the contact resistance to be a small value, the temperature isrequired to be above 350° C. If the vacuum heat-treatment temperature isabove 450° C., aluminum and Ni are excessively reacted with each other,and the surface has intensive unevenness. Therefore, the vacuumheat-treatment temperature is necessary to be 350° C. to 450° C.

FIG. 16 shows the measurement result of the sheet resistance when thevacuum degree in the vacuum heat treatment is varied. It is apparentfrom the figure that a vacuum is required to suppress the sheetresistance to a small value. That is, if any gas (oxygen, ammonia,nitrogen, etc.) exists in the environment when the ferromagneticmagnetoresistive element thin film 10 is exposed to high temperaturestate, the resistance at the bond portion (contact portion) between thealuminum wiring metal 9 and the ferromagnetic magnetoresistive elementthin film 10 is increased, and the strongly active ferromagneticmagnetoresistive element thin film 10 is oxidized, so that it can notkeep a characteristic as a magnetoresistive member. The vacuum degreemay be below about 10⁻² Torr, for example, and in this case no increasein resistance is confirmed.

FIG. 17 shows the comparative measurement result of the bond resistance(contact resistance) in a case where the vacuum heat treatment isconducted and in a case where no vacuum heat treatment is conducted. Thecontact resistance, which is the same after the ferromagneticmagnetoresistive element thin film 10 is formed, is reduced in about oneorder by conducting the vacuum heat treatment, so that the contactresistance is not varied even when the surface protection film (siliconnitride) 11 is formed by the plasma CVD and the contact resistance isreduced in three or four orders in comparison with the case ofconducting no vacuum heat treatment.

FIG. 18 shows an analysis result of the bond portion (contact portion)between the aluminum wiring metal 9 and the ferromagneticmagnetoresistive element thin film using a secondary ion massspectrometer when the vacuum heat treatment is conducted.

In comparison with the conventional result as shown in FIG. 28 when novacuum heat treatment is conducted, in the conventional result, a largeamount of aluminum nitride (AlN) exists at the contact portion, and itcauses increase in contact resistance. On the other hand, as shown inFIG. 18, the vacuum heat treatment suppresses the formation of thealuminum nitride to be half or less at the contact portion. Thismechanism will be hereunder described.

By conducting the vacuum heat treatment before the surface protectionfilm (silicon nitride) 11 is formed by the plasma CVD, an alloy layer 16of the aluminum wiring metal 9 and the ferromagnetic magnetoresistivethin film 10 is formed at the connection portion between the aluminumwiring metal 9 and the ferromagnetic magnetoresistive element thin film10 as shown in a schematic diagram of FIG. 19. This alloy layer 16serves to prohibit penetration of nitrogen component of gas reaching thesurface of the aluminum wiring metal 9 through the ferromagneticmagnetoresistive element thin film 10 when the surface protection filmis formed by the plasma CVD. Accordingly, the insulating aluminumnitride is inhibited from being formed at the connection portion betweenthe ferromagnetic magnetoresistive element thin film 10 and the aluminumwiring metal 9 when the surface protection film is formed. As a result,the increase of the contact resistance can be prevented.

Even when the N--Al-based alloy 16 is formed by conducting the vacuumheat treatment, the junction between the aluminum wiring metal 9 and theferromagnetic magnetoresistive thin film 10 is a metal contact, and thusthe equation (1) is also satisfied, so that the resistance variationrate which is a magnetic characteristic of the ferromagneticmagnetoresistive element thin film 10 is unvaried as shown in FIG. 20.

As described above, in this embodiment, the aluminum wiring metal 9having the slant section is disposed on the P-type semiconductorsubstrate 1, and in the magnetoresistive element having the Nickel-basedferromagnetic magnetoresistive element thin film 10 extending form theupper side of the slant sectional portion 9a, representing the contactresistance rate of the aluminum wiring metal 9 and the ferromagneticmagnetoresistive element thin film 10 by ρc, the inclination angle ofthe slant sectional portion 9a of the aluminum wiring metal 9 by θ, andthe thickness of thinner one of the aluminum wiring metal 9 and theferromagnetic magnetoresistive element thin film 10 at the contactportion therebetween by t and the length of the contact portion by L,the contact resistance Rc between the aluminum wiring metal 9 and theferromagnetic magnetoresistive element thin film 10 is determined sothat the following equation is satisfied: Rc=ρc.sinθ/(t.L) Therefore,the contact resistance Rc between the aluminum wiring metal 9 and theferromagnetic magnetoresistive element thin film 10 can be accuratelydetermined.

Further, the film formation is made using the vacuum deposition methodwhen the ferromagnetic magnetoresistive element thin film 10 is disposedon the aluminum wiring metal 9, and the aluminum wiring metal 9 and theferromagnetic magnetoresistive element thin film 10 are disposed so asto be contacted with each other in two or more directions at theformation time of the recess portion 12 as shown in FIG. 3, so that evenwhen variation occurs in the incident angle at the deposition time ofthe ferromagnetic magnetoresistive element thin film 10, there exists atleast one direction that no constriction occurs in the ferromagneticmagnetoresistive element thin film 10. That is, as the linearconfronting line length between the aluminum wiring metal 9 and theferromagnetic magnetoresistive element thin film 10 is made longer, thecontact area is larger. Further, if the incident angle is controlled atthe deposition time of Ni--Co, it must be set at the optimum position ofa holder in the vacuum deposition device. However, in this embodiment,such a disadvantage is avoided, and the aluminum wiring metal 9 and theferromagnetic magnetoresistive element thin film 10 can be contactedwith each other more easily and more accurately.

Further, in the case where the Ni--Co-based ferromagneticmagnetoresistive element thin film 10 is used as the magnetic sensor,the value of L is increased to reduce the value of Rc, so that theoffset voltage occurring due to variation of the resistance valuebetween bridges can be greatly reduced to 1/3 to 1/2. Further, in a casewhere this magnetic sensor is used for on-vehicle mount, if the contactresistance of Ni--Co/Al is large when a battery voltage is directlyapplied to the ferromagnetic magnetoresistive element thin film 10, thisportion may be burnt out. However, in this embodiment, the contactresistance can be set to a design value, so that such a disadvantage canbe avoided.

In the case where the ferromagnetic magnetoresistive element thin film10 is directly laminated by an electron beam deposition method after theAl sinter process (heat treatment process), the oxide layer on thesurface of the aluminum wiring metal 9 which is formed in the aluminumsinter process remains at it is. However, in this embodiment, the oxidelayer on the surface of the aluminum wiring metal 9 is first etched bythe plasma etching treatment of inert gas (for example, Ar gas), andthen the ferromagnetic magnetoresistive element thin film 10 issubjected to the electron beam deposition with keeping vacuum, so thatthe metal junction having no oxide layer is formed at the interfacebetween the ferromagnetic magnetoresistive element thin film 10 and thealuminum wiring metal 9.

Still further, in the case where the ferromagnetic magnetoresistiveelement thin film 10 is formed on the aluminum wiring metal 9 toelectrically connect the aluminum wiring metal 9 to the ferromagneticmagnetoresistive element thin film 10, and then the ferromagneticmagnetoresistive element thin film 10 is covered with the surfaceprotection film 11 formed of silicon nitride by the plasma CVD method,the vacuum heat treatment at 350° to 450° C. is conducted before thesurface protection film 11 is formed. Therefore, at the connectionportion between the aluminum wiring metal 9 and the ferromagneticmagnetoresistive element thin film 10 is formed the alloy layer 16 ofthe aluminum wiring metal 9 and the ferromagnetic magnetoresistiveelement thin film 10 in the vacuum heat treatment, and the formation ofthe insulating aluminum nitride at the connection portion when theplasma CVD is conducted is inhibited by the gas containing nitrogen. Asa result, the increase of the contact resistance between theferromagnetic magnetoresistive element thin film 10 and the aluminumwiring metal 9 due to the formation of the surface protection film 11can be inhibited.

This invention is not limited to the above embodiment. For example, inthe above embodiment, the ferromagnetic magnetoresistive element thinfilm 10 is thinner than the aluminum wiring metal 9, and thus "t" of theequation (1) is the thickness of the ferromagnetic magnetoresistiveelement thin film 10. However, when the aluminum wiring metal 9 isthinner than the ferromagnetic magnetoresistive element thin film 10,the thickness of the aluminum wiring metal 9 is "t" of the equation (1).

Further, in order to contact the aluminum wiring metal 9 with theferromagnetic magnetoresistive element thin film 10 in at least threedirections, as another manner as shown in FIG. 21, the ferromagneticmagnetoresistive element thin film 10 may be covered around the squareor rectangular aluminum wiring metal 9. That is, the contact with theside surface portion of the aluminum wiring metal 9 may be made at thebroad portion 14 of the tip side of the ferromagnetic magnetoresistiveelement thin film 10 to contact the aluminum wiring metal 9 with theferromagnetic magnetoresistive element thin film 10 in the threedirections, and the length L of the contact portion may be longer. Inthis structure, the aluminum wiring metal 9 and the ferromagneticmagnetoresistive element thin film 10 are disposed so as to be contactedwith each other in the three directions. Further, as shown in FIG. 22,the ferromagnetic magnetoresistive element thin film 10 may be coveredaround a circular aluminum wiring metal 9. In this structure, thealuminum wiring metal 9 and the ferromagnetic magnetoresistive elementthin film 10 can be contacted with each other in substantially alldirections.

Further, in the above embodiment, the case where the bipolar IC isformed on the semiconductor substrate 1 is described. However, it may beintegrated with a MOS element. FIG. 23 shows a structure that thisinvention is implemented on the C-MOS transistor. That is, a BPSG film28 is formed at the main surface side of the C-MOS structure siliconsubstrate 26 through a LOCOS oxide film 27, and the plasma siliconnitride film 29 is formed on the BPSG film 28. The ferromagneticmagnetoresistive thin film 10 of Ni--Co and the aluminum wiring metal 9are connected to each other through the Ni--Al-based alloy 16 asdescribed above on the plasma silicon nitride film 29, and covered withthe surface protection film 11 formed of plasma silicon nitride film.

Further, the vacuum heat treatment is conducted in the above embodiment,however, the heat treatment may be conducted under atmosphere of anotherinert gas (helium, argon or the like) containing no N₂.

As shown in FIG. 24, in the magnetic sensor having the ferromagneticmagnetoresistive element thin film 10 (Ni--Co thin film), this inventionmay be applied to a case where a protection resistance member 17composed of the same material as the ferromagnetic magnetoresistiveelement thin film 10 is used to protect a surge voltage, etc. for theferromagnetic magnetoresistive element thin film 10. That is, in themagnetic sensor in which the aluminum wiring metal 9 whose end portionis formed in a slant shape in section on the P-type semiconductorsubstrate 1 and the protection resistance member 17 composed of the samematerial as the ferromagnetic magnetoresistive element thin film. 10 isformed so as to extend from the upper side of the sectional slantportion 9a, the contact resistance Re may be determined from theequation (1).

Next, another embodiment will be described. In the following embodiment,an AlN insulating layer 15 which will be formed on the Al surface whenthe surface protection film 11 is omitted from the illustration.

(Second Embodiment)

FIG. 30 is a cross-sectional view of the magnetic sensor of the secondembodiment according to this invention, and the ferromagneticmagnetoresistive element thin film 10 and the signal processing circuitare integrated in the same substrate.

The second embodiment of this invention will be described in accordancewith its manufacturing process with reference to FIGS. 31 to 33. Thesame elements as the first embodiment are represented by the samereference numerals.

First, as shown in FIG.31, like the first embodiment, on the mainsurface of the P-type semiconductor substrate 1 is formed a vertical NPNbipolar transistor comprising an N⁺ -type buried layer 2, an N⁻ -typeepitaxial layer 3, an P⁺ -type diffusion region 6 and N⁺ -type diffusionregions 7 and 8. This transistor serves to amplify a signal from aferromagnetic magnetoresistive element thin film 11 as described later.

Subsequently, as shown in FIG. 1 32, conductive metal 18 of non-aluminumgroup conductor which is formed of TiW is deposited on a silicon oxidefilm 4 by a sputtering method. The film thickness is set to about 10 nmto 30 nm. This conductive metal 18 is patterned by a photoetchingtreatment,

Thereafter, an opening portion 4a is selectively formed in the siliconoxide film 4 using the photolithography to form a contact portion.Subsequently, as shown in FIG. 33, thin film aluminum wiring metal 9 isdeposited on the main surface of the P-type semiconductor substrate 1 inabout 0.1 μm, and this aluminum wiring metal 9 is patterned by thephotoetching treatment. At this time, the aluminum wiring metal 9 isdisposed so that tile end portion thereof is overlapped with the uppersurface of the end portion of the conductive metal 18. Subsequently, anohmic contact between the aluminum wiring metal 9 and the circuitelement (silicon) is formed by the heat treatment process (an alloyingtreatment is conducted).

Subsequently, the above substrate is set on the substrate holder in theelectron beam deposition apparatus. Similarly in the First embodiment,the ferromagnetic magnetoresistive element thin film 10 is deposited inabout 0.5 nm thickness by the electron beam deposition method and thenpatterned by the photoetching treatment. At this time, the ferromagneticmagnetoresistive element thin film 10 is so disposed that the endportion thereof is overlapped with the upper surface of the end portionof the conductive metal 18. The ferromagnetic magnetoresistive elementthin film 10 and the aluminum wiring metal 9 are electrically connectedto each other through the conductive metal 18.

Finally, as shown in FIG. 30, the surface protection film 11 formed ofplasma silicon nitride film is formed using the plasma CVD apparatus. Atthe film formation time of this plasma silicon nitride film, it isexposed to NH₃ gas which is one of atmosphere gases, however, no nitridelayer is formed on the surface of the conductive metal 18 formed of TiW.Further, since at the connection portion with the aluminum wiring metal9 the conductive metal 18 serves as a lower layer and thus the contactis made at the aluminum lower portion, no insulating Al--N is formed atthe contact portion. The conductive metal 18, the aluminum wiring metal9, the ferromagnetic magnetoresistive element thin film 10 and thecircuit element formed on the main surface of the P-type semiconductorsubstrate 1 are protected from the outside air by the surface protectionfilm 11.

As described above, in this embodiment, the ferromagneticmagnetoresistive element thin film 10 formed of Ni--Co, the conductivemetal 18 (non-aluminum group conductor) formed of TiW and the aluminumwiring metal 9 are disposed on the P-type semiconductor substrate 1 toelectrically connect the ferromagnetic magnetoresistive element thinfilm 10 and the aluminum wiring metal 9 with each other through theconductive metal 18, and further the ferromagnetic magnetoresistiveelement thin film 10, the conductive metal 18 and the aluminum wiringmetal 9 are covered with the surface protection film formed of plasmasilicon nitride film 11. Accordingly, the nitride layer is formed on thesurface of the aluminum wiring metal 9 under NH₃ gas atmosphere when thesurface protection film 11 is formed. However, no insulating AlN existsat the contact portion between the ferromagnetic magnetoresistiveelement thin film 10 and the conductive metal 18 and the contact portionbetween the conductive metal 18 and the aluminum wiring metal 9. Thatis, the ferromagnetic magnetoresistive element thin film 10 and thealuminum wiring metal 9 are electrically connected to each other throughthe conductive metal 18 (TiW) which does not form nitride, whereby theincrease in contact resistance of Ni--Co/Al due to formation of thesurface protection film can be inhibited.

FIG. 34 shows the measurement results of the contact resistance ofNi--Co/Al after the photoetching treatment of the ferromagneticmagnetoresistive element thin film 10 under the NH₃ gas atmosphere whichis one of atmosphere gases used when the surface protection film 11(P-SiN film) is formed, and after the plasma silicon nitride film isformed. From this figure, in the second embodiment, the increase of thecontact resistance is not found out even when exposed to the NH₃atmosphere.

As the conductive metal 18 of non-aluminum group conductor may be usedmaterial which does not form a nitride layer on the surface thereof whenthe surface protection film is formed like TiW or whose nitride film isconductive like titan nitride, and which is usable to electricallyconnect the ferromagnetic magnetoresistive element thin film 10 and thealuminum wiring metal 9 to each other and is not denatured by etchingliquid. Accordingly, as the non-aluminum group conductor (18) may beused TiW, TiN, polycrystal silicon, noble metal such as Au, Pt or thelike.

(Third Embodiment)

Next, a third embodiment will be described.

FIG. 35 is a cross-sectional view of the magnetic sensor of the thirdembodiment, and the ferromagnetic magnetoresistive element thin film 10and the signal processing are integrated in the same substrate.

FIGS. 36 to 38 show the manufacturing process thereof.

First, as shown in FIG. 36, the NPN bipolar transistor is formed in thesilicon substrate 1. Subsequently, the opening portion 4a is selectivelyformed on the silicon oxide film 4 to form the contact portion.Thereafter, the aluminum wiring metal 9 serving a first layer isdeposited on the silicon oxide film 4, and the aluminum wiring metal 9is patterned by the photoetching treatment. Further, the ohmic contactis made between the aluminum wiring metal 9 and the circuit element(silicon) through the heat treat treatment. Subsequently, the substrateas described above is set on the substrate holder inside of the electronbeam deposition apparatus, and the ferromagnetic magnetoresistiveelement thin film 10 of Ni--Co is deposited by the electron beamdeposition method, and patterned by the photoetching treatment. At thistime, the aluminum wiring metal 9 and the ferromagnetic magnetoresistiveelement thin film 10 are disposed away from each other.

Subsequently, as shown in FIG. 37, the insulating film 20 of plasmasilicon nitride film is deposited in about 0.5 μm thickness. An openingportion 20a is selectively formed in the insulating film 20 so as toextend to the aluminum wiring metal 9 and the ferromagneticmagnetoresistive element thin film 10 by the photolithography. In thisembodiment, this opening portion 20a is formed as two contact holes,however, it may be formed as one opening hole which is formed in theneighborhood of the connection portion of the aluminum wiring metal 9and the ferromagnetic magnetoresistive element thin film 10.

Thereafter, as shown in FIG. 38, a thin film of aluminum wiring metal 19serving as a second layer is deposit by the sputtering method. Beforedeposition of the aluminum wiring metal 19, the surface of the aluminumwiring metal 9 serving as the first layer and the surface of theferromagnetic magnetoresistive element thin film 10 are etched by aninverse-sputtering method. Subsequently, the aluminum wiring metal 19serving as the second layer is patterned using the photolithography. Asa result, the aluminum wiring metal 9 of the first layer and theferromagnetic magnetoresistive element are electrically connected toeach other through the aluminum wiring metal 19 of the second layer. Thethickness of the aluminum wiring metal 9 is set to about 1 μm, and thethickness of the aluminum wiring metal 19 is set to about 5000 Å. In thepatterning process of the aluminum wiring metal 19 of the second layer,an insulating film 20 is formed at the lower layer thereof, and thealuminum wiring metal 9 and the ferromagnetic magnetoresistive elementthin film 10 at the lower layer side are prevented from beingsimultaneously etched.

Finally, as shown in FIG. 35, the surface protection film 11 of plasmasilicon nitride film is formed using the plasma CVD apparatus. Theresult is exposed to the NH₃ gas which is one of the atmosphere gases inthe formation process of the plasma silicon nitride film. However, anpassive state is formed on the surface of the aluminum wiring metal 19to prevent further invasion of NH₃, and no insulating AlN exists at thecontact portion between the aluminum wiring metal 19 and theferromagnetic magnetoresistive element thin film 10, so that as shown inFIG. 34, no increase in contact resistance is not found out in thisembodiment (third embodiment) even when exposed to NH₃ atmosphere.

FIG. 39 shows an example where the structure of the third embodiment isadopted on a C-MOS transistor. That is, a BPSG film 28 is formed at amain surface side of a silicon substrate 26 of a C-MOS structure throughan LOCOS oxide film 27, and further a plasma silicon oxide film 29 isformed on the BPSG film 28. Subsequently, the ferromagneticmagnetoresistive element thin film 10 of Ni--Co is formed on the plasmasilicon oxide film 29, and the aluminum wiring metal 19 of the secondlayer is superposedly disposed on the end portion of the ferromagneticmagnetoresistive element thin film 10, so that the ferromagneticmagnetoresistive element thin film 10 and the aluminum wiring metal 19are electrically connected to each other. Further, the ferromagneticmagnetoresistive element thin film 10 and the aluminum wiring metal 19are covered by the surface protection film 11 formed of plasma siliconnitride film. In FIG. 39, a reference numeral 20 represents aninsulating film, and a reference numeral 9 represents aluminum wiringmetal of first layer.

(Fourth Embodiment)

Next, a fourth embodiment will be described.

FIG. 40 is a cross-sectional view of the magnetic sensor of the fourthembodiment, and the ferromagnetic magnetoresistive element thin film 10and the signal processing circuit are integrated in the same substrate.

FIGS. 41 to 43 show the manufacturing process thereof.

First, as shown in FIG. 41, as described in the first embodiment, theNPN bipolar transistor for amplification is formed on the siliconsubstrate 1, and the opening portion 4a is selectively formed in thesilicon oxide film 4 using the photolithography and the aluminum wiringmetal 9 of thin film is deposited. The aluminum wiring metal 9 ispatterned by the photoetching treatment to form the end portion of thealuminum wiring metal 9 in a slant shape (tapered shape) like the firstembodiment. Subsequently, the ohmic contact between the aluminum wiringmetal 9 and the circuit element (silicon) is made by aluminum sinter inthe heat treatment process, so that the oxide film grown on the surfaceof the aluminum wiring metal 9 is subjected to a sputter-etchingtreatment.

Subsequently, a barrier metal 21 of Ti (titanium) film is deposited inthickness of 100 to 3000 Å by the deposition method or the sputteringmethod. As shown in FIG. 42, the barrier metal 21 is patterned by thephotoetching treatment so that it remains on the slant-shaped region ofthe end portion of the aluminum wiring metal 9.

Thereafter, the ferromagnetic magnetoresistive element thin film 10 ofNi--Co is deposited by the deposition method. Subsequently, as shown inFIG. 43, the ferromagnetic magnetoresistive element thin film 10 issubjected to the photoetching treatment to be etched to a desired bridgepattern. At this time, the ferromagnetic magnetoresistive element thinfilm 10 is disposed on the end portion of the aluminum wiring metal 9through the barrier metal 21, so that the ferromagnetic magnetoresistiveelement thin film 10 and the aluminum wiring metal 9 are electricallyconnected to each other.

Subsequently, as shown in FIG. 40, the surface protection film 11 ofplasma silicon nitride film is deposited. In this formation process ofthe plasma silicon nitride film, the result is exposed to NH₃ gas whichis one of the atmosphere gases, and NH₃ gas or N₂ gas penetrates throughthe ferromagnetic magnetoresistive element thin film 10, so that a TiNlayer is formed on the surface of the barrier metal 21 at the interfacebetween the ferromagnetic magnetoresistive element thin film 10 and thebarrier metal 21. The TiN layer has excellent electrical conductivityand thus it shows no failure of conductivity unlike AlN. That is, thebarrier metal 21 of Ti (titanium) film is nitride to form nitride of Ti(titanium). However, the volume resistivity of Ti (titanium) isdecreased through a nitriding process of Ti (titanium), and thus nofailure of conductivity occurs at this portion. As described above, thesurface of the aluminum wiring metal 9 is not nitride through thenitriding process of the barrier metal 21. Therefore, the contactresistance between the ferromagnetic magnetoresistive element thin film10 and the aluminum wiring metal 9 can be inhibited from increasing dueto formation of the surface protection film.

As described above, in this embodiment, the barrier metal 21 of Ti(titanium) film is laminated between the ferromagnetic magnetoresistiveelement thin film 10 and the aluminum wiring metal 9 on the P-typesemiconductor substrate 1 to electrically connect the ferromagneticmagnetoresistive element thin film 10 and the aluminum wiring metal 9 toeach other, and the ferromagnetic magnetoresistive element thin film 10and the aluminum wiring metal 9 are covered by the surface protectionfilm 11 formed of plasma silicon nitride film.

Therefore, the barrier metal 21 is disposed in a laminate state betweenthe ferromagnetic magnetoresistive element thin film 10 and the aluminumwiring metal 9, and the barrier metal 21 is nitride under the NH₃ gasatmosphere when the plasma silicon nitride film is formed. However, thisnitride has low resistance, and thus the increase in contact resistanceis inhibited.

In this embodiment, the Ti (titanium) film is used as the barrier metal,however, Zr (zirconium) or the like may be used. In short, there may beused material which is not liable to be nitride by aluminum-based wiringmetal, and even when it is nitride, it has low resistance andconductive.

Further, as a modification of this embodiment, it may be embodied asshown in FIGS. 44 and 45. That is, FIG. 44 is a plane view on thesubstrate 1, and FIG. 45 is an E--E cross-sectional view. In thismodification, the barrier metal 21 is formed over the whole aluminumwiring metal 9, and a draw-out portion 21a of the barrier metal 21 isprovided on the substrate 1 so as to extend from the barrier metal 21.

(Fifth Embodiment)

Next, a fifth embodiment will be described.

FIG. 46 is a cross-sectional view of the magnetic sensor of the fifthembodiment, and the ferromagnetic magnetoresistive

- 40 element thin film 10 and the signal processing circuit areintegrated in the same substrate.

FIGS. 47 to 49 show the manufacturing process thereof.

First, as shown in Fig, 47, like the various embodiments as describedabove, the NPN bipolar transistor is formed, the opening portion 4a isselectively formed in the silicon oxide film 4 using thephotolithography, and the thin film of aluminum wiring metal 9 isdeposited on the main surface of the P-type semiconductor substrate 1.The aluminum wiring metal 9 is patterned by the photoetching treatment.At this time, the end portion of the aluminum wiring metal 9 is designedin a slant shape (tapered shape). Thereafter, the ohmic contact is madebetween the aluminum wiring metal 9 and the circuit element (silicon) inthe heat treatment process.

After this sinter process of Al (heat treatment process), the substrateas described above is set on the substrate holder inside of the vacuumchamber to etch the oxide layer grown on the surface of the aluminumwiring metal 9 by the sputter etching of inert gas (for example, Argas). Thereafter, as shown in FIG. 48, in the same vacuum chamber, theferromagnetic magnetoresistive element thin film 10 of Ni--Co issubjected to the electron beam deposition while keeping the vacuumstate. Subsequently, the ferromagnetic magnetoresistive element thinfilm 10 is etched to a desired bridge pattern by the photoetchingmethod. At this time, the ferromagnetic magnetoresistive element thinfilm 10 is disposed on the end portion of the aluminum wiring metal 9.

Subsequently, as shown in FIG. 49, the silicon oxide film 22 isdeposited by the sputtering method, and as shown in FIG. 46, the surfaceprotection film 11 of plasma silicon nitride film is deposited. In thisprocess of forming the plasma silicon nitride film, the result isexposed to NH₃ gas which is one of the atmosphere gases, however, theinvasion of NH₃ is prevented by the silicon oxide film 22, so that noinsulating AlN is formed at the contact portion between theferromagnetic magnetoresistive element thin film 10 and the aluminumwiring metal 9.

Therefore, according to the magnetic sensor thus manufactured, theferromagnetic magnetoresistive element thin film 10 of Ni--Co and thealuminum wiring metal 9 are disposed on the P-type semiconductorsubstrate 1, and the ferromagnetic magnetoresistive element thin film 10and the aluminum wiring metal 9 are electrically connected to eachother. In addition, the ferromagnetic magnetoresistive element thin film10 and the aluminum wiring metal 9 are covered with the silicon oxidefilm 22, and the silicon oxide film 22 is covered by the surfaceprotection film 11 of plasma silicon nitride film.

As a result, as shown in FIG. 34, the increase in contact resistance isnot found out in the fifth embodiment even when exposed to the NH₃atmosphere. That is, the invasion of NH₃ is prevented by the siliconoxide film 22 under the NH₃ gas atmosphere when the surface protectionfilm (plasma silicon 42 nitride film) 11 is formed, and no insulatingAlN exists at the contact portion between the ferromagneticmagnetoresistive element thin film 10 and the aluminum wiring metal 9.Therefore, using the silicon oxide film 22, the increase of contactresistance of Ni--Co/Al due to the film formation of P--SiN can beinhibited.

The silicon oxide film 22 serving as the insulating film may be formedby the electron beam deposition method in place of the sputteringmethod, and a plasma SiO or a TEOS (tetraethoxy silane) film may be usedfor the plasma method. Further, in place of the silicon oxide film 22,an amorphous silicon film by CVD may be used.

This invention is not limited to the above embodiments. For example, inthe above embodiments, Ni--Co is used for the ferromagneticmagnetoresistive element thin film, however, another ferromagneticmagnetoresistive element thin film, particularly a Ni-based thin film(Ni--Fe, Ni--Fe--Co, or the like) may be used. Further, as thealuminum-based wiring metal may be used not only pure aluminum, but alsoaluminum group material such as Al--Si, Al--Si--Cu or the like.

Further, in the above embodiments, the silicon nitride film (Si_(x)N_(y)) is described as the surface protection film. However, anothernitride film such as SiON or the like may be used as the protectionfilm. Further, as the protection film, the upper layer of the abovenitride film may be covered by a polyimide film as a final protectionfilm.

Still further, in the above embodiments, the aluminum wiring issubjected to the plasma etching treatment to purify the surface thereofafter the heat treatment process (sinter process). However, the aluminumsurface is easily formed with an oxide layer by washing it even when thesurface of aluminum may be exposed to the outside air, and thus theseoxide layers containing the above oxide layer may be removed before theferromagnetic magnetoresistive element thin film 10 is formed.

Still further, the above various embodiments are described with respectto the magnetic sensor formed on the bipolar transistor. However, theseembodiments may be applied to a magnetic sensor which is integrated withan MOSFET such as C-MOS, N-MOS, Bi-CMOS or the like. Further, theseembodiments may be applied to a discrete magnetic sensor which is sodesigned as to be formed on a silicon substrate formed with a glasssubstrate and an insulating layer.

INDUSTRIAL APPLICABILITY

As described above, according to the magnetoresistive element of thisinvention, even when the surface protection film is formed of siliconnitride, the increase in contact resistance between the magnetoresistiveelement thin film and the wiring metal due to the formation of thesurface protection film can be inhibited, and thus the magnetoresistiveelement thin film having low contact resistance can be obtained.Accordingly, the resistance value of the magnetoresistive element can beaccurately obtained, and silicon nitride having excellentmoisture-resistance as the surface protection film can be used.Therefore, the magnetic sensor using this magnetoresistive element thinfilm is very effectively applied to the case where it is integrated witha controlling or amplifying semiconductor element in the same substrate.

We claim:
 1. A magnetoresistive element comprising:an aluminum-basedwiring metal disposed on said substrate; a nickel-based magnetoresistiveelement thin film disposed on said substrate such that a portion of saidnickel-based magnetoresistive element thin film overlaps a portion ofsaid aluminum-based wiring metal, said nickel-based magnetoresistiveelement thin film being electrically connected to said aluminum-basedwiring metal at said overlap; a barrier film disposed between saidnickel-based magnetoresistive element thin film and said aluminum-basedwiring metal to protect said aluminum-based wiring metal from nitrogen,wherein said barrier film is an alloy layer of said nickel-basedmagnetoresistive element thin film and said aluminum-based wiring metal;and a surface protection film of nitride that covers said nickel-basedmagnetoresistive element thin film.
 2. A magnetoresistive elementcomprising:a substrate; an aluminum-based wiring metal disposed on saidsubstrate; a nickel-based magnetoresistive element thin film disposed onsaid substrate such that a portion of said nickel-based magnetoresistiveelement thin film overlaps a portion of said aluminum-based wiringmetal, said nickel-based magnetoresistive element thin film beingelectrically connected to said aluminum-based wiring metal at saidoverlap, wherein an end portion of said aluminum-based wiring metal atsaid overlap defines a contact portion between said nickel-basedmagnetoresistive element thin film and said aluminum-based wiring metal,said end portion of said aluminum-based wiring metal having bevelededges and having a recessed portion defined therein so as to maximize alength of said contact portion a barrier film disposed between saidnickel-based magnetoresistive element thin film and said aluminum-basedwiring metal to protect said aluminum-based wiring metal from nitrogen;and a surface protection film of nitride that covers said nickel-basedmagnetoresistive element thin film.
 3. A magnetoresistive elementcomprising:a substrate; an aluminum-based wiring metal disposed on saidsubstrate and having a connection region defined thereon; a nickel-basedmagnetoresistive element thin film disposed on said substrate such thata portion of said nickel-based magnetoresistive element thin filmoverlaps at least a portion of said connection region of saidaluminum-based wiring metal; a barrier film disposed between saidnickel-based magnetoresistive element thin film and said aluminum-basedwiring metal, said barrier film having a consistency such that saidbarrier film is impermeable to nitrogen, wherein said barrier film is aaluminum-based metal film which covers said connection region; and asurface protection film of nitride that covers said nickel-basedmagnetoresistive element thin film.
 4. The magnetoresistive elementaccording to claim 3, wherein said aluminum-based metal film serves asan electrically connecting member between said nickel-basedmagnetoresistive element thin film and said aluminum-based wiring metal.5. A magnetoresistive element comprising:a substrate; an aluminum-basedwiring metal disposed on said substrate and having a connection regiondefined thereon; a nickel-based magnetoresistive element thin filmdisposed on said substrate such that a portion of said nickel-basedmagnetoresistive element thin film overlaps at least a portion of saidconnection region of said aluminum-based wiring metal, wherein saidconnection region is located at an end portion of said aluminum-basedwiring metal at said overlap between said nickel-based magnetoresistiveelement thin film and said aluminum-based wiring metal, said end portionof said aluminum-based wiring metal having beveled edges and having arecessed portion defined therein so as to maximize a length of saidconnection region; a barrier film disposed between said nickel-basedmagnetoresistive element thin film and said aluminum-based wiring metal,said barrier film having a consistency such that said barrier film isimpermeable to nitrogen; and a surface protection film of nitride thatcovers said nickel-based magnetoresistive element thin film.
 6. Amagnetoresistive element comprising:a substrate; an aluminum-basedwiring metal disposed on said substrate; a nickel-based magnetoresistiveelement thin film disposed on said substrate; a connection conductorwhich electrically connects said aluminum-based wiring metal to saidnickel-based magnetoresistive element thin film and is disposed at afirst side of said aluminum-based wiring metal and a first side of saidnickel-based magnetoresistive element thin film, wherein said first sideof said aluminum-based wiring metal is a side of said aluminum-basedwiring metal proximate to said substrate, and said first side of saidnickel-based magnetoresistive element thin film is a side of saidnickel-based magnetoresistive element thin film proximate to saidsubstrate; and a surface protection film of nitride that covers saidnickel-based magnetoresistive element thin film.
 7. The magnetoresistiveelement according to claim 6, wherein said connection conductor is aselected from a group consisting of titanium tungsten, titanium nitride,polycrystalline silicon, gold and platinum.
 8. A magnetoresistiveelement comprising:a substrate; an aluminum-based wiring metal disposedon said substrate, an upper surface of said aluminum-based wiring metalincluding a contacting portion; a nickel-based magnetoresistive elementthin film disposed on said substrate and on said contacting portion ofsaid aluminum-based wiring metal such that said nickel-basedmagnetoresistive element thin film is electrically connected to saidaluminum-based wiring metal, wherein said contacting portion is locatedat an end portion of said aluminum-based wiring metal at an overlapbetween said nickel-based magnetoresistive element thin film and saidaluminum-based wiring metal, said end portion of said aluminum-basedwiring metal having beveled edges and having a recessed portion definedtherein so as to maximize a length of said contacting portion; a barrierfilm interposed said nickel-based magnetoresistive element thin film andsaid aluminum-based wiring metal at said contacting portion, saidbarrier film having a consistency such that said barrier film isimpermeable to nitrogen; and a surface protection film of nitride thatcovers said nickel-based magnetoresistive element thin film.